1. Field of the Invention
The present invention relates to ink jet printing devices of the type disclosed for example, in Sweet et al. U.S. Pat. Nos. 3,373,437 and Taylor et al. RE. 28,219, and more particularly to a charging plate and method of fabrication thereof for use in an ink jet printing head as disclosed, for example, in Beam et al. U.S. Pat. Nos. 3,586,907 and Houser 3,701,476.
2. Prior Art
One of the most common methods presently used for fabricating charge plates is by drilling or otherwise forming holes in a plate made of dielectric material, in properly spaced relation so that the holes will be in alignment with corresponding orifices formed in the orifice plate of an ink jet printing device. A series of discrete lines of electrically conductive coating material are formed on the plate and around each hole. Such a charge plate is disclosed for example in U.S. Pat. No. 3,586,907. These charge plates can easily be fabricated by conventional printed circuit techniques, however, the precision required in spacing and aligning of the holes as well as properly positioning the discrete conductive lead lines extending around and from each hole, is somewhat difficult to achieve especially in a repeatable manner as is required for high volume production.
In still further attempts to produce charge plates with evenly spaced charging faces or electrodes, a variety of methods of configuring a solid, single piece of substrata to provide a series of U-shaped channels along the edge portion thereof have also been devised. These charge plates are generally provided with charging surfaces in at least the base portion as well as along the sides of the U-shaped channels by using photo-fabrication or similar technique to plate a conductive material along the surface of the solid substrata. This technique, however, still requires extremely accurate machining techniques in order to form the channels at evenly spaced intervals along the edge of the substrata. The precision required results in this type of method being fairly expensive as well as difficult and time consuming to produce.
A still further attempt to produce uniformly spaced charging surfaces in a solid substrata involves the use of crystaline material such as silicone which has specific crystal orientation and can thus be etched to produce uniformly spaced channels along the surface or edge of a single piece which can then be secured by adhesive or otherwise to a larger support plate. This method does produce a series of uniformly spaced surfaces which can then be plated with a conductive material to provide uniformly spaced charging surfaces associated with orifice positions.
However, because of the fixed nature of the crystaline structure in such materials the positioning between adjacent orifices must be maintained in accordance with the required spacing for the etching of the material as is established by the crystaline structure thereof. Therefore, this produces a limitation upon the density of orifice spacing and/or requires the spacing to be established on the basis of the spacing of the charging surfaces which will result from the specific crystaline structure of the charge plate so fabricated. Thus, a loss in flexibility of density of orifice spacing occurs due to the limitations of the substrata material.